TWI740730B - Tungsten trioxide/silicon nanocomposite structure, manufacturing method thereof and gas sensing device - Google Patents

Abstract

A method for manufacturing a tungsten trioxide/silicon nanocomposite structure includes steps as follows. A silicon substrate is provided, wherein a surface of the silicon substrate is formed with a plurality of microstructures. A tungsten trioxide precursor solution is provided, wherein the tungsten trioxide precursor solution is contacted with the silicon substrate. A hydrothermal synthesis step is conducted, wherein the tungsten trioxide precursor solution is reacted to form a plurality of tungsten trioxide particles on the plurality of microstructures, so as to obtain the tungsten trioxide/silicon nanocomposite structure.

Description

Tungsten trioxide/silicon nano composite structure, its manufacturing method and gas sensing device

The present invention relates to a tungsten trioxide (WO ₃ )/silicon (Si) nanocomposite structure, its manufacturing method and a gas sensing device containing the same, and in particular to a low-cost WO ₃ /Si nanocomposite structure , Its manufacturing method, and a gas sensing device containing the same.

Air pollution refers to the presence of at least one air pollutant in the atmosphere, and the concentration of the air pollutant is sufficient to affect the health of humans, animals, and plants for a duration. Take nitrogen oxides (NO _X ) as an example. NO _X is a common air pollutant. NO _X contains gases such as nitric oxide (NO) and nitrogen dioxide (NO ₂ ), which are the main components of acid rain and are Catalyzed by sunlight, volatile substances are produced, which can cause human respiratory diseases, and have a negative impact on the environment and human health. Therefore, how to monitor the concentration of air pollutants has recently attracted much attention.

Metal oxide semiconductor materials refer to metal oxides, such as zinc oxide (ZnO), tin oxide (SnO ₂ ), WO _3, etc., which have semiconductor characteristics due to structural defects. When gas molecules adsorb on the surface of the metal oxide semiconductor material, the conductivity will change. Therefore, the concentration of gas molecules can be inferred by measuring the resistance change. Therefore, metal oxide semiconductor materials are widely used in gas sensing. Device. Most of the gas sensing devices using metal oxide semiconductor materials on the market use sputtering to deposit metal oxides on the surface of the substrate in the form of particles to form a sensing film. However, the sputtering method requires an electric field to generate high-energy accelerated particles to bombard the target in a vacuum state, and the equipment has a high threshold, which leads to high costs.

Object of the present invention is to provide a WO ₃ / Si nano composite structure, manufacturing method thereof and comprising a gas sensing device which is to solve the above problems.

According to one embodiment of the present invention to provide a method of manufacturing a nano WO ₃ Si / composite structure, comprising the following steps. A silicon substrate is provided, wherein a plurality of microstructures are formed on a surface of the silicon substrate. Provide a WO ₃ precursor to make the WO ₃ precursor contact the silicon substrate. A hydrothermal synthesis step is carried out to react the WO ₃ precursor liquid to form a plurality of WO ₃ particles on the microstructure to obtain a WO ₃ /Si nanocomposite structure.

According to the aforementioned WO ₃ /Si nanocomposite structure manufacturing method, it may further include a drying step to remove _{moisture from the WO 3} /Si nanocomposite structure.

According to the aforementioned WO ₃ /Si nanocomposite structure manufacturing method, it may further include a plasma modification step in which an oxygen-containing plasma is used to modify the surface _{of the WO 3 /Si nanocomposite structure.}

According to the aforementioned WO ₃ /Si nanocomposite structure manufacturing method, each microstructure can be a nanowire. The length of the nanowire can be 400 nm to 1400 nm, and the width of the nanowire can be 40 nm to 500 nm.

According to the aforementioned WO ₃ /Si nanocomposite structure manufacturing method, the WO ₃ precursor preparation method may include the following steps. An aqueous solution containing tungstate is provided, wherein the aqueous solution containing tungstate contains tungstate and water. An acidification step is performed by adding an acidic substance to the aqueous solution containing tungstate to obtain the WO ₃ precursor. The concentration of tungstate in the aqueous solution containing tungstate may be 0.002M to 1.8M. Tungstate can be provided by sodium tungstate. The aqueous solution containing tungstate may further contain a dispersant. The concentration of the dispersant in the tungstate-containing aqueous solution can be 0.004M to 0.4M. The dispersant may be sodium chloride.

According to the aforementioned WO ₃ /Si nanocomposite structure manufacturing method, the acid-base value (pH value) of the _{WO 3 precursor can be 0-6.}

According to the aforementioned WO ₃ /Si nanocomposite structure manufacturing method, the hydrothermal synthesis step can be performed in a heating device, and the hydrothermal synthesis step can include a temperature rising stage, a temperature holding stage, and a cooling stage. The heating stage is to raise the heating device to a predetermined temperature at a predetermined rate, the temperature holding stage is to keep the heating device at a predetermined temperature for a predetermined time, and the cooling stage is to cool the heating device from a predetermined temperature to room temperature. The aforementioned predetermined rate may be 3°C/min to 10°C/min, the predetermined temperature may be 140°C to 250°C, and the predetermined time may be 4 to 8 hours.

According to the aforementioned WO ₃ /Si nanocomposite structure manufacturing method, the silicon substrate can be set in a jig, the jig includes two covering parts and a holding part, the silicon substrate is arranged between the two covering parts, and the holding part clamps Two covering parts are held to fix the silicon substrate between the two covering parts. There may be a gap between the two covering parts, and the WO ₃ precursor can be dropped into the gap between the two covering parts to contact the silicon substrate.

According to another embodiment of the present invention is to provide a WO ₃ / Si nano composite structure produced by the preceding-based production method is obtained.

According to the aforementioned WO ₃ /Si nanocomposite structure, _{the particle size of each WO 3} particle can range from 5 nanometers to 100 nanometers.

According to another embodiment of the present invention, a gas sensing device is provided, which includes the aforementioned WO ₃ /Si nanocomposite structure.

Based on the gas sensing means, wherein the gas sensing means for sensing the NO _X.

Compared with the prior art, the WO ₃ /Si nanocomposite structure manufacturing method of the present invention uses a silicon substrate with a microstructure as a substrate, which is beneficial to increase the surface area of the surface to which the _{WO 3 particles are attached.} The manufacturing method of the WO ₃ /Si nanocomposite structure of the present invention uses a hydrothermal synthesis step to form WO ₃ particles on a silicon substrate. Compared with the sputtering method, it is beneficial to reduce the cost. In the method of manufacturing WO ₃ /Si nanocomposite structure of the present invention, the silicon substrate can be preferably placed in a jig, and the WO ₃ precursor liquid can be brought into contact with the silicon substrate by means of dripping, thereby avoiding the hydrothermal synthesis During the step, WO ₃ reunites itself to form a film. The method for manufacturing WO ₃ /Si nanocomposite structure of the present invention can preferably undergo a plasma modification step, thereby increasing _{the oxygen vacancy on the surface of WO 3} /Si nanocomposite structure. When applied to gas The sensing device is beneficial to improve the responsiveness of sensing gas at room temperature.

100: _{Manufacturing method of WO 3} /Si nanocomposite structure

110~150: Step

200: WO ₃ /Si nanocomposite structure

210: Silicon substrate

211: Surface

212: Microstructure

220: WO ₃ particles

311: Cover

312: Clamping parts

320: Dropper

330: WO ₃ precursor fluid

400: Preparation method of _{WO 3 precursor}

410~420: steps

D: particle size

G: gap

L: length

W: width

Fig. 1 is a flow chart of the manufacturing method of _{WO 3} /Si nanocomposite structure according to an embodiment of the present invention.

Figure 2 is a schematic diagram of _{converting a silicon substrate into a WO 3} /Si nanocomposite structure through a hydrothermal synthesis step according to an embodiment of the present invention.

_{FIG. 3 is a schematic top view of the WO 3} precursor in contact with the silicon substrate according to an embodiment of the present invention.

Figure 4 is a flow chart of the steps of _{a WO 3} precursor preparation method according to an embodiment of the present invention.

Figure 5 is a scanning electron microscope (Scanning Electron Microscope, SEM) photograph _{of a WO 3} /Si nanocomposite structure according to an embodiment of the present invention.

FIG. 6 is a graph showing the test results of the gas sensing responsivity of the _{WO 3} /Si nanocomposite structure at room temperature according to an embodiment of the present invention.

FIG. 7 is a graph showing the test results of the gas sensing responsivity of the _{WO 3} /Si nanocomposite structure at room temperature according to another embodiment of the present invention.

<WO ₃ /Si nanocomposite structure manufacturing method>

Please refer to FIG. 1, which is a flow chart of the manufacturing method 100 of _{WO 3 /Si nanocomposite structure according to an embodiment of the present invention.} In Figure 1, _{the manufacturing method 100 of WO 3} /Si nanocomposite structure includes steps 110 to 130, and may optionally include step 140 and step 150. Step 110 is to provide a silicon substrate, wherein a plurality of microstructures are formed on a surface of the silicon substrate. Specifically, the silicon substrate can be single crystal silicon, and can optionally be doped with other elements, such as group IIIA elements or group VA elements, that is, the silicon substrate can be a P-type silicon substrate or an N-type silicon substrate.

_{Please refer to FIG. 2, which is a schematic diagram of converting a silicon substrate 210 into a WO 3} /Si nanocomposite structure 200 through a hydrothermal synthesis step according to an embodiment of the present invention. As shown in Figure 2, a surface 211 of the silicon substrate 210 is formed with a plurality of microstructures 212. Here, a linear nanowire with the microstructure 212 is taken as an example. However, the present invention is not limited to this. 212 is used to increase the surface area. Therefore, in other embodiments, the microstructure 212 can be configured as a curved nanowire, a hole structure or other types, and the effect of increasing the surface area can also be achieved. In Figure 2, the length L of the nanowire can be 400 nm to 1400 nm, and the width W of the nanowire can be 40 nm to 500 nm, which is beneficial to improve the response to the sensed gas. . Preferably, the length L of the nanowire can be 800 nanometers to 1200 nanometers, and the width W of the nanowire can be 100 nanometers to 200 nanometers. For example, the silicon substrate 210 can be manufactured using a metal-assisted chemical etching (Metal-assisted Chemical Etching) process, that is, a silicon wafer with a smooth surface (without microstructure) is provided first, and the silicon wafer is etched using metal-assisted chemical etching. The surface of the wafer is obtained, and a silicon substrate 210 with a plurality of microstructures 212 formed on the surface 211 is obtained. How to form microstructures on silicon wafers is well known in the art, and will not be repeated here.

Please refer to FIG. 1 again. In step 120, a WO ₃ precursor is provided so that the WO ₃ precursor contacts the silicon substrate.

With reference to FIG. 3, it is a _{schematic top view of the WO 3} precursor 330 in contact with the silicon substrate 210 according to an embodiment of the present invention. In Figure 3, the silicon substrate 210 is set in a jig (not otherwise marked). The jig includes two covering members 311 and two clamping members 312. The silicon substrate 210 is set between the two covering members 311, and the clamping member 312 clamps The two covering members 311 are held to fix the silicon substrate 210 between the two covering members 311. Here, the number of the clamping members 312 is illustrated as two, however, the present invention is not limited to this, and the number of the clamping members 312 can be adjusted according to actual needs. Two cover having a gap G between the member 311, WO ₃ precursor solution was added dropwise 330 may be in contact with the gap G between the two cover members 311 and 210 and the silicon substrate. Specifically, the two covering members 311 may have a sheet-like structure and may be respectively disposed on two opposite sides of the silicon substrate 210 to sandwich the silicon substrate 210 therebetween. The clamping member 312 is used to fix the two covering members 311 and the silicon substrate 210. , And provide the pressure required for the subsequent hydrothermal synthesis step. In other words, the pressure that the silicon substrate 210 is placed between the clamps is greater than the atmospheric pressure. In addition, the clamping force of the clamping member 312 can be adjusted according to actual needs to adjust the pressure that the silicon substrate 210 is placed between the clamps. The WO ₃ precursor 330 can be contained in a dropper 320, and the dropper 320 is used to drop the WO ₃ precursor 330 from the gap G between the two covering members 311 to contact the silicon substrate 210. By using a clamp, the WO ₃ precursor 330 can be prevented from forming a thin film during the hydrothermal synthesis step, and it is advantageous _{to distribute the WO 3} on the microstructure 212 in the form of particles, thereby improving the responsiveness to the sensing gas. By dropping the WO ₃ precursor 330 into contact with the silicon substrate 210, the WO ₃ precursor 330 can be quickly and uniformly distributed on the surface of the silicon substrate 210, and the total amount of the _{WO 3 precursor 330 can be controlled.}

Please refer to FIG. 4, which is a flow chart of the preparation method 400 of _{WO 3 precursor according to an embodiment of the present invention.} In Fig. 4, _{the preparation method 400 of WO 3} precursor liquid includes step 410 and step 420.

Step 410 is to provide an aqueous solution containing tungstate, wherein the aqueous solution containing tungstate contains tungstate and water. The aqueous solution containing tungstate may optionally further contain a dispersant for improving the dispersibility of tungstate in water, avoiding _{agglomeration during subsequent formation of WO 3} particles, so as to improve _{the dispersibility of WO 3} particles in the microstructure. In the aqueous solution containing tungstate, the concentration of tungstate may be 0.002M to 1.8M, and the concentration of the dispersant may be 0.004M to 0.4M. According to one embodiment of the present invention, tungstate can be provided by sodium tungstate (Na ₂ WO ₄ ), for example, sodium tungstate dihydrate ((Na ₂ WO ₄ ˙2H ₂ O) can be dissolved in water to obtain tungstate, However, the present invention is not limited to this. Any material that is soluble in water and can provide tungstate can be used as the source of tungstate. The dispersant can be sodium chloride, however, the present invention is not limited thereto. Any substance that is soluble in water and does not react with tungstate can be used as a dispersant.

Step 420 is to perform an acidification step, which is to add an acidic substance to the aqueous solution containing tungstate to obtain the WO ₃ precursor. The acidic substance is used to adjust the pH value so that the pH value of the prepared WO ₃ precursor solution is within a predetermined range, and the hydrogen ions in the acidic substance can combine with tungstate to form tungstic acid. The pH value of the WO ₃ precursor solution can be 0 to 6, so that the subsequent formation of WO ₃ particles has better responsiveness for sensing gas. Preferably, _{the pH value of the WO 3} precursor liquid may be 0.4 to 2. The acidic substance may be a hydrochloric acid (HCl) aqueous solution, however, the present invention is not limited to this, and any acidic substance that does not react with the silicon substrate and tungstic acid can be used as the acidic substance in step 420. In addition, the WO ₃ precursor is used to transform into WO ₃ particles in the hydrothermal synthesis step. Therefore, _{the preparation method 400 of the WO 3} precursor is only an example, and the present invention is not limited to this, as long as it is in the hydrothermal synthesis step The WO ₃ precursor liquid that can be converted into WO ₃ particles is within the protection scope of the present invention.

Please refer to Figure 1 again. In step 130, a hydrothermal synthesis step is performed to react the WO ₃ precursor to form a plurality of WO ₃ particles on the microstructure to obtain a WO ₃ /Si nanocomposite structure. Please refer to Figure 2 again. In the WO ₃ /Si nanocomposite structure 200, the WO ₃ particles 220 are dispersed on a plurality of microstructures 212. _{The particle size D of the WO 3} particles 220 can range from 5 nm to 100 nm. Therefore, the WO ₃ particles 220 have excellent responsivity for sensing gas.

According to an embodiment of the present invention, the hydrothermal synthesis step can be performed in a heating device, and can include a heating stage, a temperature holding stage, and a cooling stage. The heating stage is to increase the heating device to a predetermined temperature at a predetermined rate. The temperature holding stage is to keep the heating device at a predetermined temperature for a predetermined time, and the cooling stage is to cool the heating device from a predetermined temperature to room temperature. According to an embodiment of the present invention, the heating device can be a hydrothermal kettle, and the silicon substrate and the WO ₃ precursor are directly placed in the hydrothermal kettle. According to another embodiment of the present invention, the silicon substrate is set in a jig (see Figure 3). At this time, the heating device can be, but not limited to, a high-temperature furnace. Specifically, when WO _{3 is dropped into the silicon substrate in the jig} After the precursor liquid, the silicon substrate can be heated in a high-temperature furnace together with the fixture. The aforementioned predetermined rate may be 3°C/min to 10°C/min, the predetermined temperature may be 140°C to 250°C, and the predetermined time may be 4 to 8 hours. Regarding the condition parameters of the hydrothermal synthesis step, it can be adjusted according to the type and size of the microstructure of the silicon substrate, the concentration of the _{WO 3 precursor solution, and the size of the WO 3} particles to be generated.

FIG. 1, step 140 is performed a drying step for removing water which is a WO ₃ / Si nano-composite structure. For example, the heating means may be removed by the WO ₃ / Si nano composite structure is placed in an oven, carried out in 60 ℃ 10 hours. However, the temperature and time of the drying step can be adjusted according to actual conditions, as long as the temperature is not high enough to damage the WO ₃ /Si nanocomposite structure and remove water.

In Figure 1, step 150 is a plasma modification step, which uses an oxygen-containing plasma to _{modify the surface of the WO 3} /Si nanocomposite structure. Oxygen-containing plasma means that the gas source that forms the plasma contains oxygen. According to one embodiment of the present invention, the WO ₃ /Si nanocomposite structure can be placed in a plasma cleaning machine, evacuated and an oxygen-containing gas is introduced to form an oxygen-containing plasma. ₃ /Si nanocomposite structure undergoes surface modification for a predetermined time. For example, the plasma cleaner can be evacuated to about 0.01torr, the oxygen-containing gas can use oxygen, the flow rate of oxygen into the plasma cleaner can be 6sccm (standard cubic centimeter per minute), the power can be set to 20W, the aforementioned predetermined time It may be 10 seconds to 120 seconds, and preferably, the aforementioned predetermined time may be 40 seconds to 80 seconds. Through step 150, _{oxygen vacancy on the surface of the WO 3} /Si nanocomposite structure can be increased. When applied to a gas sensing device, it is beneficial to improve the responsiveness of sensing gas at room temperature.

<WO ₃ /Si nanocomposite structure>

The present invention provides a WO ₃ /Si nanocomposite structure, which is manufactured using the manufacturing method 100 of _{WO 3 /Si nanocomposite structure.}

As shown in Figure 2, the WO ₃ /Si nanocomposite structure 200 according to the present invention includes a silicon substrate 210 and a plurality of WO ₃ particles 220. A surface 211 of the silicon substrate 210 is formed with a plurality of microstructures 212, WO ₃ The particles 220 are distributed on a plurality of microstructures 212. The WO ₃ /Si nanocomposite structure 200 is responsive to a specific gas, and can be used to sense the specific gas. Regarding the WO ₃ /Si nanocomposite structure 200, please refer to the relevant description above. Regarding the application of the WO ₃ /Si nanocomposite structure 200 for gas sensing, please refer to the relevant description below, which will not be repeated here.

<Gas Sensing Device>

The present invention provides a gas sensing device, which system contains WO ₃ / Si nano composite structure. The WO ₃ /Si nanocomposite structure is responsive to specific gases. The specific gases include, but are not limited to, NO _x , NH ₃ , and acetone vapor. The NO _x can be, but is not limited to, NO ₂ . When the composite structure of WO ₃ / Si is preferably subjected to nano plasma modification step, may further enhance the WO ₃ / Si nano composite structure for a particular gas at room temperature responsiveness of the WO ₃ / Si nano composite structure in The specific gas can be sensed at room temperature. In other words, the gas sensing device according to the present invention may preferably be a room temperature gas sensing device. Specifically for example, WO ₃ / Si nano composite structure of the present invention on the NO ₂ at room temperature with excellent responsiveness it can be used to detect NO ₂ at room temperature.

<Preparation of Examples>

Provide a silicon substrate (step 110). The manufacturing method of the silicon substrate is as follows: Take a P-type silicon wafer, cut it into a 2cm×2cm square test piece, and soak it in the first acid etching solution for 15 seconds. And the second acid etching solution for 1 minute. The preparation method of the first acidic etching solution is to add silver nitrate and hydrofluoric acid to deionized water, wherein the concentration of silver nitrate is 0.01M and the concentration of hydrofluoric acid is 4.6M. The preparation method of the second acidic etching solution is to add hydrogen peroxide and hydrofluoric acid to deionized water, wherein the concentration of hydrogen peroxide is about 0.035M and the concentration of hydrofluoric acid is 4.6M. The reaction of the square test piece in the first acid etching solution is as shown in formula (1) to formula (3), and the reaction of the square test piece in the second acid etching solution is as shown in formula (4) to formula (5): ^{4Ag + +4 e - → 4Ag (} 1); Si + 2H 2 O → SiO 2 + 4H + + 4e - (2); SiO 2 + 6HF → H 2 SiF 6 + 2H 2 O (3); H 2 O _{^{2 + 2H + → 2H 2 O}} + 2h + (4); 2H + + 2e - → H 2 ↑ (5).

Provide a WO ₃ /Si precursor (step 120). _{The preparation method of the WO 3} /Si precursor is as follows: Provide an aqueous solution containing tungstate (step 410), and take appropriate amounts of Na ₂ WO ₄ ˙2H ₂ O and NaCl to The deionized water is dissolved to form an aqueous solution containing tungstate, in which _{the concentration of Na 2} WO ₄ ˙2H ₂ O is 0.02M and the concentration of NaCl is 0.04M. Carry out an acidification step (step 420), drop a 12M HCl aqueous solution into the tungstate-containing aqueous solution until the pH value is about 1.2 to obtain a WO ₃ /Si precursor solution. The reaction of the acidification step is shown in formula (6): WO ₄ ^2- +2H ⁺ → H ₂ WO ₄ ↓ (6).

Set the silicon substrate in the jig (refer to Figure 3), where the glass slide is used as the cover, and the long tail clip is used as the holding piece, and the WO ₃ /Si precursor is dropped from the gap between the two glass slides. Into contact with the silicon substrate.

Place the silicon substrate and fixtures in a high-temperature furnace for the hydrothermal synthesis step (step 130). First, the temperature is raised to 160°C at a rate of 5°C/min, and the temperature is maintained at 160°C for about 6 hours, and then the heating is stopped to bring the temperature After cooling to room temperature, a WO ₃ /Si nanocomposite structure is obtained.

A drying step (step 140) is performed, and the WO ₃ /Si nanocomposite structure is taken out from the high-temperature furnace and separated from the fixture, placed in an oven, and dried at 60° C. for 10 hours to remove moisture. The surface morphology of the dried WO ₃ /Si nanocomposite structure was observed by SEM, and the gas sensing response test was performed. Please refer to the following for the results.

Carry out a plasma modification step (step 150), place the WO ₃ /Si nanocomposite structure in a plasma cleaner (Basic Plasma Cleaner, Harrick Plasma, PDG-32G), and vacuum to about 0.01torr, with 6sccm Oxygen was introduced at a flow rate of 20W for 60 seconds, and a gas sensing response test was performed. For the results, please refer to the following.

<Sexual Quality Test of Example>

_{The WO 3} /Si nanocomposite structure after the drying step was observed with SEM, and the result is shown in Figure 5. In Figure 5, the microstructure of the silicon substrate is nanowires, WO ₃ /Si particles are formed on the microstructure, and _{the particle size of the WO 3} /Si particles is 5 nm to 100 nm.

_{The WO 3} /Si nanocomposite structure that has undergone the drying step is subjected to a gas sensing response test at room temperature (25° C.), and the result is shown in Figure 6. Specifically, Figure 6 is the measurement of the WO ₃ /Si nanocomposite structure for ethanol (EtOH), isopropanol (IPA), acetone (Acetone) and other vapors and ammonia (NH ₃ ) at a concentration of 25 ppm. The response value, and the response value of nitrogen dioxide (NO ₂ ) at a concentration of 3 ppm, where the WO ₃ /Si nanocomposite structure has a response value of 1 for isopropanol vapor, that is, the WO ₃ /Si nanocomposite structure is for isopropyl Alcohol vapor does not have responsiveness, but the order of responsiveness to other substances is as follows: NO ₂ > ammonia gas> ethanol vapor> acetone vapor. Among them _{, the responsiveness to NO 2} is the most excellent, and _{the tested concentration of NO 2} is much lower than others. Substance, however, has the highest response value.

_{The WO 3} /Si nanocomposite structure that has undergone the plasma modification step was tested for gas sensing response at room temperature, and the results are shown in Figure 7. Comparing Figure 6 and Figure 7, after the plasma modification step, the WO ₃ /Si nanocomposite structure has a significant increase in response to ethanol, isopropanol, acetone and other vapors, ammonia, and NO _2. The WO ₃ /Si nanocomposite structure changed from being non-responsive to isopropanol vapor, and _{the response value to NO 2} increased significantly from 1.25 to 3.49.

_{The WO 3} /Si nanocomposite structure that has undergone the plasma modification step is _{further tested for its sensing limit for NO 2} at room temperature, and it is obtained that the sensing limit of the WO ₃ /Si nanocomposite structure for NO ₂ is 151 ppb. In other words, when _{the concentration of NO 2} in the air is very low, the WO ₃ /Si nanocomposite structure according to the present invention can still sense the presence of _{NO 2.}

It can be seen from the test results in Fig. 6 and Fig. 7 that the WO ₃ /Si nanocomposite structure of the present invention is responsive to specific gases and can be applied to sense specific gases. WO invention ₃ / Si nano composite structure after the step of plasma modification can greatly enhance the responsiveness of a specific gas at room temperature, but may be applied to gas-temperature sensing means. In addition, the WO ₃ /Si nanocomposite structure of the _{present invention has excellent response to NO 2} at room temperature and excellent sensing limit, and can be applied to detect NO ₂ at room temperature.

Compared with the prior art, the WO ₃ /Si nanocomposite structure manufacturing method of the present invention uses a silicon substrate with a microstructure as a substrate, which is beneficial to increase the surface area of the surface to which the _{WO 3 particles are attached.} The manufacturing method of the WO ₃ /Si nanocomposite structure of the present invention uses a hydrothermal synthesis step to form WO ₃ particles on a silicon substrate. Compared with the sputtering method, it is beneficial to reduce the cost. In the method of manufacturing WO ₃ /Si nanocomposite structure of the present invention, the silicon substrate can be preferably placed in a jig, and the WO ₃ precursor liquid can be brought into contact with the silicon substrate by means of dripping, thereby avoiding the hydrothermal synthesis During the step, WO ₃ reunites itself to form a film. The manufacturing method of the WO ₃ /Si nanocomposite structure of the present invention can preferably undergo a plasma modification step, whereby _{the oxygen vacancy on the surface of the WO 3} /Si nanocomposite structure can be increased. When applied to a gas sensing device, It is helpful to improve the responsiveness of sensing gas at room temperature.

The foregoing descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made in accordance with the scope of the patent application of the present invention shall fall within the scope of the present invention.

100: Manufacturing method of tungsten trioxide/silicon nanocomposite structure

110~150: Step

Claims (18)

A method for manufacturing a tungsten trioxide/silicon nanocomposite structure includes: providing a silicon substrate, wherein a plurality of microstructures are formed on a surface of the silicon substrate; providing a tungsten trioxide precursor solution to make the tungsten trioxide precursor solution Contacting the silicon substrate; and performing a hydrothermal synthesis step to cause the tungsten trioxide precursor to react to form a plurality of tungsten trioxide particles on the microstructures to obtain the tungsten trioxide/silicon nanocomposite structure; The hydrothermal synthesis step is performed in a heating device, and the hydrothermal synthesis step includes: a heating stage, which causes the heating device to rise to a predetermined temperature at a predetermined rate; and a temperature holding stage, which causes the heating device to rise to a predetermined temperature Maintaining at the predetermined temperature for a predetermined time; and a cooling stage in which the heating device is cooled from the predetermined temperature to room temperature; wherein the predetermined rate is 3°C/min to 10°C/min, and the predetermined temperature is 140 ℃ to 250 ℃, the predetermined time is 4 to 8 hours. The manufacturing method of the tungsten trioxide/silicon nanocomposite structure as described in claim 1, further comprising: performing a drying step to remove moisture from the tungsten trioxide/silicon nanocomposite structure. The manufacturing method of the tungsten trioxide/silicon nanocomposite structure as described in claim 1, further comprising: performing a plasma modification step in which an oxygen-containing plasma is used to perform the tungsten trioxide/silicon nanocomposite structure Surface modification. The method for manufacturing a tungsten trioxide/silicon nanocomposite structure according to claim 1, wherein each of the microstructures is a nanowire. The method for manufacturing a tungsten trioxide/silicon nanocomposite structure according to claim 4, wherein a length of the nanowire is 400 nm to 1400 nm, and a width of the nanowire is 40 nm to 500 Nano. The manufacturing method of the tungsten trioxide/silicon nanocomposite structure according to claim 1, wherein the preparation method of the tungsten trioxide precursor liquid comprises: providing an aqueous solution containing tungstate, wherein the aqueous solution containing tungstate contains tungstate and Water; and an acidification step is to add an acidic substance to the tungstate-containing aqueous solution to obtain the tungsten trioxide precursor solution. The method for manufacturing a tungsten trioxide/silicon nanocomposite structure according to claim 6, wherein the concentration of the tungstate in the aqueous solution containing tungstate is 0.002M to 1.8M. The method for manufacturing a tungsten trioxide/silicon nanocomposite structure according to claim 6, wherein the tungstate is provided by sodium tungstate. The method for manufacturing a tungsten trioxide/silicon nanocomposite structure according to claim 6, wherein the aqueous solution containing tungstate further contains a dispersant. The method for manufacturing a tungsten trioxide/silicon nanocomposite structure according to claim 9, wherein the concentration of the dispersant in the tungstate-containing aqueous solution is 0.004M to 0.4M. The method for manufacturing a tungsten trioxide/silicon nanocomposite structure according to claim 9, wherein the The dispersant is sodium chloride. The manufacturing method of the tungsten trioxide/silicon nanocomposite structure according to claim 1, wherein the acid-base value (pH value) of the tungsten trioxide precursor is 0-6. The method for manufacturing a tungsten trioxide/silicon nanocomposite structure according to claim 1, wherein the silicon substrate is set in a jig, the jig includes two covering members and a clamping member, and the silicon substrate is set on the two Between the covering pieces, the clamping piece clamps the two covering pieces to fix the silicon substrate between the two covering pieces. The method for manufacturing a tungsten trioxide/silicon nanocomposite structure according to claim 13, wherein there is a gap between the two covering members, and the tungsten trioxide precursor is dripped between the two covering members through the gap. Make contact with the silicon substrate. A tungsten trioxide/silicon nanocomposite structure manufactured by the manufacturing method according to any one of claims 1 to 14. The tungsten trioxide/silicon nanocomposite structure according to claim 15, wherein the particle size of each tungsten trioxide particle is 5 nanometers to 100 nanometers. A gas sensing device comprising the tungsten trioxide/silicon nanocomposite structure as described in claim 15. The gas sensing device according to claim 17, wherein the gas sensing device is used for sensing Nitrogen oxides.

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